Stargate Atlantis - Tango by astolat. John, who's pretty sure he's straight, notices that Rodney comes up with solutions to problems faster after an orgasm. So for the good of the city/team/mission/expedition, he starts providing Rodney with them.

Doujinshi Examples

Naruto- カタコイ編 (Katakoi Hen) Unrequited Love Compilation, L4R - There is one story in which Kakashi orders Iruka to have sex with him while on a mission. Kakairu.